Ozone reducing heat sink having contoured fins

ABSTRACT

Ion wind fans generate ozone. To more effectively catalyze ozone, in one embodiment, the present invention includes a heat sink having contoured heat sink fins that are coated with an ozone catalyst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/233,112 filed Aug. 11, 2009, the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The embodiments of the present invention are related to ion wind fans, and in particular to a collector electrode for an ion wind fan.

BACKGROUND

It is well known that heat can be a problem in many electronics device environments, and that overheating can lead to failure of components such as integrated circuits (e.g. a central processing unit (CPU) of a computer) and other electronic components. Most electronics devices, from LED lighting to computers and entertainment devices, implements some form of thermal management to remove excess heat.

Heat sinks are a common passive tool used for thermal management. Heat sinks use conduction and convection to dissipate heat and thermally manage the heat-producing component. To increase the heat dissipation of a heat sink, a conventional rotary fan or blower fan has been used to move air across the surface of the heat sink, referred to generally as forced convection. Conventional fans have many disadvantages when used in consumer electronics products, such as noise, weight, size, and reliability caused by the failure of moving parts and bearings.

A solid-state fan using ionic wind to move air addresses the disadvantages of conventional fans. However, providing an ion wind fan that meets the requirements of consumer electronics devices presents numerous challenges not addressed by any currently existing ionic wind device. For example, ozone (O₃) generated by an ion wind fan may need to be mitigated.

Ozone is a pollutant produced by ionic fans. It can cause some adverse health effects and is regulated by numerous government agencies. In addition, ozone has a strong odor that is considered unpleasant at any but the lowest concentration. At very low concentrations, however, ozone is either undetectable by humans or may give the sense of a “fresh and clean” environment.

Ozone produced by an ionic fan can be removed by a catalysis reaction. A common catalyst is Manganese Oxide (MnO), but other known catalysts exist, such as Platinum, Manganese Dioxide, Iodonium, and Titanium Dioxide. When ozone contacts the catalyst it is converted back into normal oxygen (0₂).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an ion wind fan implemented as part of thermal management of an electronic device;

FIG. 2A is a perspective view of an ion wind fan according to one embodiment of the present invention;

FIG. 2B is a widthwise cross-sectional view of the ion wind fan of FIG. 2A according to one embodiment of the present invention;

FIG. 3 is a top view block diagram of an ion wind fan and a heat sink coated with an ozone catalyst;

FIG. 4 is a perspective view of an ion wind fan according to one embodiment of the present invention;

FIG. 5 is a perspective view of an ion wind fan according to another embodiment of the present invention;

FIG. 6 is a top view block of an ion wind fan and an upstream heat sink and a downstream heat sink according to one embodiment of the present invention;

FIGS. 7A-C are side views of various fin contours according to various embodiments of the present invention;

FIG. 8A-C are side views of various heat sinks created using the fins of FIGS. 7A-C, according to various embodiments of the present invention;

FIG. 9A-B are top view block diagrams of an ion wind fan and a heat sink according to various embodiments of the present invention;

FIG. 10 is a block diagram of an ion wind fan and a metal foam ozone destroyer according to one embodiment of the present invention; and

FIG. 11 is a block diagram of an ion wind fan in a fan enclosure coated with ozone catalyst according to one embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. In the present specification, an embodiment showing a singular component should not necessarily be so limited; rather the principles thereof can be extended to other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.

Ion wind or corona wind generally refers to the gas flow that is established between two electrodes, one sharp and the other blunt, when a high voltage is applied between the electrodes. The air is partially ionized in the region of high electric field near the sharp electrode. The ions that are attracted to the more distant blunt electrode collide with neutral (uncharged) molecules en route to the collector electrode and create a pumping action resulting in air movement. The high voltage sharp electrode is generally referred to as the emitter electrode or corona electrode, and the grounded blunt electrode is generally referred to as the counter electrode, getter electrode, or collector electrode.

The general concept of ion wind—also sometimes referred to as ionic wind and corona wind even though these concepts are not entirely synonymous—has been known for some time. For example, U.S. Pat. No. 4,210,847 to Shannon, et al., dated Jul. 1, 1980, titled “Electric Wind Generator” describes a corona wind device using a needle as the sharp corona electrode and a mesh screen as the blunt collector electrode. The concept of ion wind has been implemented in relatively large-scale air filtration devices, such as the Sharper Image Ionic Breeze.

Example Ion Wind Fan Thermal Management Solution

FIG. 1 illustrates an ion wind fan 10 used as part of a thermal management solution for an electronic device. As used in this Application, the descriptive term “ion wind fan,” is used to refer to any electro-aerodynamic pump, electro-hydrodynamic (EHD) pump, EHD thruster, corona wind device, ionic wind device, or any other such device used to move air or other gas. The term “fan” refers to any device that move air or some other gas. The term ion wind fan is meant to distinguish the fan from conventional rotary and blower fans. However, any type of ionic gas movement can be used in an ion wind fan, including, but not limited to corona discharge, dielectric barrier discharge, or any other ion generating technique.

An electronic device may need thermal management for an integrated circuit—such as a chip or a processor—that produces heat, or some other heat source, such as a light emitting diode (LED). Some example systems that can use an ion wind fan for thermal management include computers, laptops, gaming devices, projectors, television sets, set-top boxes, servers, NAS devices, memory devices, LED lighting devices, LED display devices, smart-phones, music players and other mobile devices, and generally any device having a heat source requiring thermal management.

The electronic device can have a system power supply 16 or can receive power directly from the mains AC via a wall outlet, Edison socket, or other outlet type. For example, in the case of a laptop computer, the laptop will have a system power supply such as a battery that provides electric power to the electronic components of the laptop. In the case of a wall-plug device such as a gaming device, television set, or LED lighting solution (lamp or bulb), the system power supply 16 will receive the 110V mains AC (in the U.S.A, 220V in the EU) current from an electrical outlet or socket.

The system power supply 16 for such a plug or screw-in device will also convert the mains AC into the appropriate voltage and type of current needed by the device (e.g., 20-50V DC for an LED lamp). While the system power supply 16 is shown as separate from the IWFPS 20, in some embodiments, one power supply can provide the appropriate voltage to both an ion wind fan 10 and other components of the electronic device. For example, a single driver can be design to drive the LEDs of and LED lamp and an ion wind fan included in the LED lamp.

The electronic device also includes a heat source (not shown), and may also include a passive thermal management element, such as a heat sink (also not shown). To assist in heat transfer, an ion wind fan 10 is provided in the system to help move air across the surface of the heat source or the heat sink, or just to generally circulate air (or some other gas) inside the device. In prior art systems, conventional rotary fans with rotating fan blades have been used for this purpose.

As discussed above, the ion wind fan 10 operates by creating a high electric field around one or more emitter electrodes 12 resulting in the generation of ions, which are then attracted to a collector electrode 14. In FIG. 1, the emitter electrodes 12 are represented as triangles as an illustration that they are generally “sharp” electrodes. However, in a real-world ion wind fan 10, the emitter electrodes 12 can be implemented as wires, shims, blades, pins, and numerous other geometries. Furthermore, while the ion wind fan 10 in FIG. 1 has three emitter electrodes (12 a, 12 b, 12 c), the various embodiments of the present invention described herein can be implemented in conjunction with ion wind fans having any number of emitter electrodes 12.

Similarly, the collector electrode 14 is shown simply as a plate in FIG. 1. However, a real-world collector electrode 14 can have various shapes and will generally include openings to allow the passage of air. The collector electrode 14 can also be implemented as multiple collector electrode members (e.g., rods, washers) held at substantially the same potential. Furthermore, in a real world ion wind fan 10, the emitter electrodes 12 and the collector electrode 14 would be disposed on a dielectric chassis—sometimes referred to as an isolator element—that has also been omitted from FIG. 1 for simplicity and ease of understanding.

To create the high electric field necessary for ion generation, the ion wind fan 10 is connected to an ion wind power supply 20. The ion wind power supply 20 is a high-voltage power supply that can apply a high voltage potential across the emitter electrodes 12 and the collector electrode 14. The ion wind fan power supply 20 (hereinafter sometimes referred to as “IWFPS”) is electrically coupled to and receives electrical power from the system power supply 16. Usually for electronic devices, the system power supply 16 provides low-voltage direct current (DC) power. For example, a laptop computer system power supply would likely output approximately 5-12V DC, while the power supply for an LED light fixture would likely output approximately 20-70V DC.

The high voltage DC generated by the IWFPS 20 is then electrically coupled to the emitter electrodes 12 of the ion wind fan 10 via a lead wire 17. The collector electrode 14 is connected back to the IWFPS 20 via return/ground wire 18, to ground the collector electrode 14 thereby creating a high voltage potential across the emitters 12 and the collector 14 electrodes. The return wire 18 can be connected to a system, local, or absolute high-voltage ground using conventional techniques.

While the system shown in and described with reference to FIG. 1 uses a positive DC voltage to generate ions, ion wind can be created using AC voltage, or by connecting the emitters 12 to the negative terminal of the IWFPS 20 resulting in a “negative” corona wind. Embodiments of the present invention are not limited to positive DC voltage ion wind. Furthermore, while the IWFPS 20 is shown to receive power from a system power supply 30, in other embodiment, the IWFPS 20 can receive power directly from an outlet.

The IWFPS 20 may include other components. Furthermore, in some embodiments, some of the components listed above may be omitted or replaced by similar or equivalent circuits. For example, the IWFPS 20 is described only as an example. Many different kinds and types of power supplies can be used as the IWFPS 20, including power supplies that do not have a transformers or other components shown in FIG. 1. The components described need not be physically separate, and may be combined on a single printed circuit board (PCB).

An example of an ion wind fan is now described with reference to FIGS. 2A and 2B. FIG. 2A is a perspective view of an example ion wind fan 30. The ion wind fan 30 includes a collector electrode 32 having air passage openings 33 to allow airflow. This example ion wind fan 30 has two emitter electrodes 36 implemented as wires, thus implementing what is sometimes referred to as a “wire-to-plane” configuration.

The collector electrode 32 and the emitter electrodes 36 are both supported by an isolator 34. The isolator is made of a dielectric material, such as plastic, ceramic, and the like. The “isolator” component is thusly named as it functions to electrically isolate the emitter electrodes 36 from the collector electrode 32, and to physically support these electrodes. As such the isolator also can establish the spatial relationship between the electrodes, sometimes referred to under the rubric of electrode geometry. The isolator 34 can be made from one integral piece—as shown in FIG. 2A—or it can be made of multiple parts and pieces.

In the embodiment shown in FIG. 2A, the collector electrode is attached to the isolator using a fastener 31. The fastener 31 in FIG. 2 is a stake, but any other attachment method can be used, including but not limited to screws, hooks, glue, and so on. Similarly, the particular method of attachment of the emitter electrodes 36 is not essential to the embodiments of the present invention. The emitter electrodes 36 can be glued, staked, screwed, tied, held by friction, or attached in any other way to the isolator 34.

The ion wind fan 30—in the embodiment shown in FIG. 2A—is substantially rectangular in top view. The longitudinal axis of the ion wind fan 30 is denoted with the dotted arrow labeled “A.” The ion wind fan 30 has two ends opposite each other along the longitudinal axis. The emitter electrodes 36 are suspended between the two ends of the ion wind fan 30.

In one embodiment, the emitter electrodes 36 are supported at the ends of the ion wind fan 30 by an emitter support 38 portion of the isolator 34. The emitter support 38 a at the left end of the ion wind fan 30 is most visible in FIG. 2A. The emitter support 38 a is a portion of the isolator that physically supports the emitter electrodes 36. In one embodiment, the emitter electrodes 36 are suspended (in tension) between the two emitter supports 38 at the two ends of the ion wind fan 30.

In the embodiment shown in FIG. 2A, the isolator 34 has two elongated members oriented along the longitudinal direction that support the collector electrode 32, and the two elongated members are held joined by two cross-members that support the emitter electrodes 36. In one embodiment, these cross-members are oriented perpendicular to the elongated members (and thus the longitudinal axis). In FIG. 2A, these cross-members make up the emitter supports 38.

Thus, while in one embodiment the emitter support 38 a is a substantially rectangular solid portion of the isolator 34 that connects the two elongated side portions of the isolator 34, in other embodiments the emitter supports 38 can have many other shapes and orientations. For example, a part of the center portion of the emitter support 38 a between the emitter electrodes 36 could be cut away without substantially affecting the function of the emitter support 38 a.

The emitter support 38 a is shown as extending to the end of the ion wind fan 30. However, in other embodiments, the emitter support 38 a can end before the end of the ion wind fan 30. The emitter support 38 a is also shown as having a curved section at its outside edge to smooth out the 90 degree bend in the wire emitter electrodes 36. This is an optional feature not related to the embodiments of the present invention described herein.

Indeed, the actual attachment of the emitter electrodes 36 to either the emitter support 38 or some other portion of the isolator 34 is not material to the embodiments of the present invention, and therefore will not be discussed in much detail for simplicity and ease of understanding. The emitter electrodes 36 are shown as extending downward from the left end of the ion wind fan 30 and they are connected to the power supply via some wire or bus, as is the collector electrode 32. The emitter supports 38 need not have any particular shape of contact with the emitter electrodes 36. The emitter supports 38 are the portions of the isolator 34 that define the physical spatial relationship between the emitter electrodes 34 and other components of the ion wind fan 30. How exactly the emitter supports 38 are in contact with the emitter electrodes 36 (grooves, stakes, friction, posts, welding, epoxy) are not germane to the embodiments of the present invention.

FIG. 2B further illustrates the example ion wind fan 30 shown in FIG. 2A. FIG. 2B is a perspective cross sectional view of the ion wind fan 30 along the line B-B shown in FIG. 2A. The emitter electrodes 36 are suspended in air, and held a substantially constant air gap 39 distance away from the collector electrode 32.

Though wire sag and other emitter irregularities will create some variance, in one embodiment the air gap 39 between the emitter electrodes 36 and the bottom plane of the collector electrode 32 is substantially constant (within a 5% variation). In other embodiments, the air gap 39 can be more variable. The size of the air gap 39 is dependent on the spatial relationship between the electrodes established by the emitter supports 38 (which are not visible in FIG. 2B).

Strategically Located Heat Sink Fins

In one embodiment of the present invention, the catalyst is only placed in areas of maximum ozone production and concentration. The catalyst has a cost associated with it for the expensive material used, and for the decreased heat dissipation of the heat sink where it is coated with the catalyst. One theoretical reaction model developed by the Applicants predicts that Ozone is highly concentrated downstream of the corona electrodes of the EHD fan. Thus, according to one embodiment—as shown in FIG. 4—special catalyst coated fins are added to a heat sink at a location directly downstream of each corona electrode. For example, in the case of a wire-type corona electrode, the high concentration region will be a long, thin-sheet-like region in the wake of the corona electrode. A catalyst coated fin in this region is predicted to remove ozone at a greater rate at than any other location. Conventional heat sinks do not generally employ horizontal fins not in this manner, as they are not the most efficient configuration for heat dissipation.

Additional fins can be added to conduct/convect heat in any direction. In one embodiment—such as the example shown in FIG. 5—the additional fins can also be coated with the catalyst, to further increase the Ozone removal capacity of the heatsink. The system removes ozone more efficiently than a system without specially located fins. The improved ozone destruction occurs without substantially increasing the flow resistance or impacting the heat transfer rate of the cooling system. In one embodiment, shown in FIGS. 4 and 5, the corona electrodes are positioned such that they run parallel to the Ozone fins in the plane of the Ozone fins. In other words, the electrodes are not positioned in the middle of the channels of the heat sink, but rather by the walls of the channels through which air is forced by the EHD fan. In another embodiment, the corona electrodes are positioned substantially in the center of the channels.

Upstream Heat Sink

The rate of ozone production in an EHD fan is reduced at elevated temperatures. If the air were pre-heated prior to reaching the EHD fan, then the EHD fan will produce less ozone. Less ozone production in the fan means less ozone to remove at the catalyst-coated downstream heat sink. In one embodiment, as shown in FIG. 6, pre-heating the air is accomplished by splitting the heat sink into two sections or by using two different kinds of heat sinks. The upstream section pre-heats the air entering the EHD fan, while simultaneously removing heat from a heat-producing element (not pictured) thermally coupled to the heat sink. The downstream section dissipates the remaining heat and catalyzes the ozone. In such an embodiment, the reduction in ozone production is accomplished without substantially impacting the flow or heat transfer properties of the heat sink. Additionally, some EHD fans operate more efficiently at elevated temperatures. Efficiency tends to increase as the square root of the absolute temperature, provided that the gas is not in a thermal plasma state (less than approximately 5000 Kelvin). Thus, this system actually can use less energy than some systems of the configuration shown in. The upstream heat sink need not be coated with the ozone catalyst.

Staggered Heat Sink Fins

An embodiment that improves the ozone catalyzing effectiveness of the fins is shown in 9A. In this embodiment the fins downstream are offset from the fins upstream. This breaks up the boundary layer and puts the ozone in more intimate contact with the catalyst. The staggered fins will also improve the heat dissipation of the heat sink. However, this embodiment exhibits a higher flow resistance and requires additional pumping energy.

An embodiment that increases the total surface area of fins is shown in 9B. In this embodiment additional fins are placed in between a “normal” finned heat sink. The extra surface area will catalyze more ozone. However, like the previous embodiment, it will have a higher resistance to flow.

Another embodiment, shown in FIG. 10, with a large amount of surface area per unit volume is a metal foam heat sink. Metal foam heat sinks are known to be compact heat transfer devices. Coating the metal with catalyst will also make an effective ozone destroyer.

Catalyst Coating of Ion Wind Fan Enclosure

A typical cooling system is located within an enclosure of some type, example: inside the case of a laptop computer or inside some other electronics consumer device, such as an LED light bulb or other lighting device. An embodiment is shown in FIG. 11 where the enclosure is also coated with the ozone catalyst. This embodiment further reduces ozone levels inside the enclosure and minimizes the detrimental effects associated with ozone production. In one embodiment, the heat sink is located inside an air directing enclosure, in which case this enclosure can be coated. In other embodiments, other components of the consumer electronics product can be catalyst coated that are in the proximity of the EHD fan. Some example components that can be coated in this manner with no substantial interference to their usual operation include the chassis, metal housings, plastic housings, ad even portions of a PCB board of a consumer electronics device, such as a laptop, monitor, projector, DVD player, storage device, gaming device, entertainment device, computer, handheld, PDA, LED light bulb, and so on.

Heat Sink Fin Shaping

Ozone destruction is limited by the surface area coated with the catalyst. Prior art heat sinks are generally constructed as a fin-stack of planar fins, such as the fin shown in FIG. 7A. The resulting heat sink formed by stacking such fins is shown in FIG. 8A. FIG. 8A shows a heat source, a flat heat spreader or base in thermal contact with the heat source, and a stack of the fins shown in FIG. 7A in thermal contact with the base. The base and the fin stack can be formed in one piece. This creates a heat sink with rectangular-shaped channels having parallel walls, as shown in FIG. 8A.

Such a straight-finned heat sink—as shown in FIG. 8A—designed only for heat transfer has a limited amount of surface area for ozone catalysis for the volume of the heat sink. Thus, in one embodiment of the present invention, additional surface area can be incorporated into the same volume by contouring the fins. For example, FIG. 7B shows a heat sink fin having four more bends then the straight heat sink fin shown in FIG. 7A. This effectively increases the surface area of the fin without increasing the volume of the space it occupies.

In one embodiment, a heat sink can be created by stacking multiple contoured heat sink fins having the shape shown in FIG. 7B in the conventional stacking manner. In yet another embodiment, described with reference to FIG. 8B, a heat sink is formed by having one row of the “hexagonal” fins from FIG. 7B facing one direction followed by a row of hexagonal fins facing the opposite direction or orientation. The rows are placed in order in the direction of the airflow. As can be seen in FIG. 8B, this arrangement forms hexagonal shaped air passage channels in addition to other shapes.

In yet another embodiment, as shown in FIG. 7B, a heat sink fin having five addition bends then the straight heat sink fin shown in FIG. 7A can be used. This increases the surface area of the fin even further without increasing the volume of the space it occupies.

In one embodiment, a heat sink can be created by stacking multiple contoured heat sink fins having the shape shown in FIG. 7C in the conventional stacking manner. In yet another embodiment, described with reference to FIG. 8C, a heat sink is formed by having one row of the “diamond” fins from FIG. 7C facing one direction followed by a row of diamond fins facing the opposite direction or orientation. The rows are placed in order in the direction of the airflow. As can be seen in FIG. 8C, this arrangement forms diamond shaped air passage channels in addition to other shapes.

In yet another embodiment, the fins have a wavelike profile, thus increasing surface area. Such fins can be arranged to form teardrop shaped channels if stacked in opposing facing rows, as explained above. Many additional shapes, contours, and channel geometries are possible.

While the heat sinks shown in FIGS. 8B and 8C will have more flow resistance than the heat sink shown in FIG. 8A and will likely be thermally inferior, such heat sinks have two key advantages that make them especially suited for ion wind fans. When placed downstream from ion wind fans, they provide additional surface area to be coated with ozone catalyst, which can mitigate ozone generation. Furthermore, when placed upstream of an ion wind fan, the complex and non-parallel channel shapes can act as a filter to filter dust fibers or other fibrous material from the air, before it does damage to the ion wind fan.

While the example ion wind fan described and pictured above are shown as having two emitter electrodes, any number of emitter electrodes can be used, including one, to create one or more-channel ion wind fans. While most electronics cooling applications using a wire emitter will have between 1-10 emitter electrodes, the invention is not limited to any range of emitter electrodes used.

In the descriptions above, various functional modules are given descriptive names, such as “ion wind fan power supply.” The functionality of these modules can be implemented in software, firmware, hardware, or a combination of the above. None of the specific modules or terms—including “power supply” or “ion wind fan”—imply or describe a physical enclosure or separation of the module or component from other system components.

Furthermore, descriptive names such as “emitter electrode,” “collector electrode,” and “isolator,” are merely descriptive and can be implemented in a variety of ways. For example, the “collector electrode,” can be implemented as one piece of metallic structure, but it can also be made of multiple members spaced apart, and connected by wires or other electrical connections to the same voltage potential, such as ground.

Similarly, the isolator can be the substantially frame-like component shown in FIG. 2A, but it can have various shapes. The electrodes and the isolator are not limited to any particular material; however, the isolator will generally be made of a dielectric material, such as plastic, ceramic, and other known dielectrics. Thus in one embodiment, any of the collector electrodes discussed herein can be substituted for the collector electrode 32 of FIG. 2A to create an ion wind fan according to an embodiment of the present invention. In other embodiments, other isolator designs can be used, as long as it establishes substantially the same spatial relationships between the electrodes. 

1. A heat sink comprising: a base in thermal contact with a heat source; a first set of fins protruding from the base, the first set of fins having a contoured non-planar shape oriented in a first direction; and a second set of fins protruding from the base, the second set of fins having a contoured shape substantially similar to the contoured non-planar shape of the first set of fins, the second set of fins being oriented in a second direction, wherein the second direction is opposite to the first direction.
 2. The heat sink of claim 1, wherein the first set of fins comprises and ozone catalyzing coating.
 3. The heat sink of claim 2, wherein the second set of fins comprises and ozone catalyzing coating. 